Thank you for this opportunity to present my assessment of a reported cluster of cancer-­‐cases among soccer players using synthetic turf fields. In what follows, I begin by addressing what is known, and not known, about these cancer-­‐cases. I also present the causal hypothesis raised by Dr. David Brown (the former Chief of Environmental Epidemiology and Occupational Health in the State of Connecticut) and his colleagues at the nonprofit group, Environment and Human Health, Inc. (EHHI). Next, I summarize what is known about cancer in adolescents, focusing on previously reported and investigated cancer-­‐clusters. I then return to EHHI’s hypothesis, and point out its central flaws. In this context, I rely on measurements of chemicals emitted from crumb rubber, turf fibers, and/or synthetic turf field-­‐
systems, as well as on quantitative exposure-­‐assessments and health risk-­‐assessments that have been based on these measurements. All such assessments have found that plausible risks of developing cancer from playing on synthetic turf fields range from none to negligible. Reports of cancer in young soccer players In May of last year, a Seattle, Washington TV station broadcast a story, “Toxic Turf? UW coach draws connection between turf and cancer.” The story noted: University of Washington assistant soccer coach Amy Griffin sees a troubling connection between the turf and cancer among soccer players. Griffin [said] . . . that 13 players from the state of Washington were all diagnosed with rare types of cancer. Of those 13, 11 were goalkeepers. Griffin can't say why goalkeepers are getting cancer but she wonders if it could be caused by the crumb rubber, a kind of filler in turf fields. . . . ‘Everyone says it's just a coincidence and kind of walks away, but the ratio of goalkeepers to field players is 15 to 1, 16 to 2, and I know plenty of goalkeepers that have cancers and I don't know many field players,’ Griffin said . . . Other news reports followed, with additional cancers reported; but, to my knowledge, no systematic or scientific study of these cases has been performed or published. Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 2 Environment and Human Health, Inc. (EHHI), however, has kept a running tally. At http://www.ehhi.org/turf/cancer_cases_grow_0115.shtml, in a recent (apparently January 2015) but undated posting, EHHI writes the following: Cancer cases among student athletes playing on synthetic turf continue to grow There are now reported 95 cancers among student athletes who have played on synthetic turf fields. 65 are soccer goal keepers (this is not surprising as goal keepers are more heavily exposed to crumb rubber). The reported cancers are: 40 lymphomas 16 leukemias 7 Brain 6 Thyroid 7 Sarcomas 3 Testicular The rest are rare forms of cancers. It is important to note the predominance of lymphomas and leukemias. 1,3 butadiene is connected to lymphoma and benzene is connected to leukemia. Both of these chemicals are present in rubber tires. The United States itself is still not tracking cancers among students who have played on synthetic turf -­‐ the U.S. government has still not tested synthetic turf for anything but lead -­‐-­‐ for which there is very little -­‐-­‐ we still have no government official asking for a congressional hearing on synthetic turf -­‐ and the government is still promoting synthetic turf with rubber tire infill at both the state and the federal levels. Synthetic turf fields are loaded with carcinogens -­‐ so no one should be surprised at the growing number of cancers among student athletes. Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 3 The surprise is that government refuses to act. When will state and federal governments step in and protect our children? And in an earlier posting, at http://www.ehhi.org/turf/brown_stc_response.shtml, EHHI writes, . . . it is known that there are carcinogens and other toxic materials in the crumb rubber and possibly other infills, that children ingest the crumbs, track them into school rooms, school buses, private cars and homes. What is not known regarding these cancers in soccer players As noted above, these cancer-­‐cases have not been reported on in any scientific journal, and no details have been reported. We do not know, for example, the ages, sexes, or races of any of the cases, nor do we know the specific forms of leukemia, lymphoma, or other cancer for any individual soccer-­‐player. Lacking this information, it is not possible to determine whether the cases constitute an actual cluster — that is, whether, as a group, they have experienced a significantly larger incidence of cancer-­‐cases than would be expected, based on rates in the general population. EHHI notes a “predominance of lymphomas and leukemias,” but these are among the most common types of cancer that develop in children and adolescents (Ward et al., 2014), and so are not necessarily noteworthy. Moreover, although cancers in young people are not common, in 2014 in the U.S., almost 16,000 children and adolescents (from 0 to 19 years of age) were expected to have been diagnosed with some form of cancer (Ward et al., 2014). Thus, learning about many cancer diagnoses in adolescents (I am assuming that most of these cases are in fact among adolescents) would not be entirely unexpected. Suppose that these 95 cases do represent a cluster — that there are indeed significantly more cases of cancer among soccer players than one would “expect.” Does this mean that the cluster has an identifiable cause? In fact, no. As explained below, many cancer clusters have been evaluated in great detail, and for almost none has a cause ever been Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 4 found. Results of prior investigations of cancer clusters For several reasons, unusual coincidences of cancers among groups of younger people are noteworthy, and many of these have been extensively investigated. However, exhaustive study of such clusters in young people has never established an environmental or other exogenous cause: these clusters appear to be due instead to random bad luck (Caldwell, 1990; Gawande, 1999; Trumbo, 2000; Connecticut Department of Health, 2012). Here, for example, is what noted epidemiologist Glynn Caldwell (1990) wrote toward the end of his long career: Beginning in 1961, the Centers for Disease Control investigated 108 cancer clusters and reported the findings in Epidemic Aid Reports. The clusters studied were of leukemia (38%), leukemia and lymphoma (30%), leukemia and other cancer combinations (13%), and all other cancer or combinations (19%). These clusters occurred in 29 states and five foreign countries . . . Eight different data collection methods were used, often in combinations, and four types of laboratory methods on four different specimen types. Although 14 different categories of associations were reported, no clear cause was found for any cluster. A priori, then, an association between playing soccer on synthetic turf fields and risk of leukemia and lymphoma may be reported, but that does not mean that the association is causal, as opposed to coincidental. Of course, some clusters of cancer in communities are due to shared environmental and carcinogenic exposures, so one cannot and should not over-­‐generalize. For example, clusters of skin cancer (and other diseases) have been repeatedly reported among groups of people who drink water that has been (naturally) contaminated with high concentrations of arsenic, and this is because such exposures are genuinely carcinogenic (IARC, 1980). Similarly, clusters of lung cancer and of mesothelioma occur in communities with naturally large amounts of erionite (a mineral similar to asbestos) in Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 5 local rocks and soils, and, again, these associations are known to be causal (IARC, 1987). Importantly, however, no community-­‐based cluster of any of the cancers at issue here has been found to have an identifiable, external, chemical cause. Another reason to doubt an external, chemical cause for adolescent cancers is this: the type of leukemia prevalent in childhood (namely, acute lymphocytic leukemia), all types of lymphomas, and brain tumors are not known to be caused by cigarette smoking (IARC, 2004). Of course, cigarette smoke is the most chemically complex and important cause of cancers of several tissues and organs (not only the lung) in the world (Surgeon General’s Report, 2014; IARC, 2004). Since chronic exposure to such a potent mixture of carcinogenic chemicals does not cause the cancers at issue, then on what reliable basis could it be suggested that the much smaller doses of some of the same chemicals (potentially) emanating from used rubber particles could cause these cancers? I can think of none. Some salient features of lymphomas, leukemias, and other cancers that occur in adolescents As noted above, EHHI reports that of the 95 cases of cancer in soccer players, 40 are cases of lymphoma. Lymphomas are not uncommon cancers: in 2014, more than 760,000 Americans were diagnosed with a form of lymphoma (Leukemia & Lymphoma Society, 2015). Among adolescents who develop cancer, lymphomas are the most common type (IARC, 2008). Dogs are also prone to developing lymphoma, with some breeds more likely to develop this cancer than other breeds (Teske, 1994). There are many different types of lymphomas, and these vary substantially with regard to their prevalence, genetic pre-­‐dispositions, other risk-­‐factors, and clinical courses (Swerdlow et al., 2008; Morton et al., 2014). (This is one reason that the lack of detail about these cases makes their interpretation difficult). As suggested by the patterns of lymphomas in dog-­‐breeds, and in some human families, some lymphoma-­‐types have a strong genetic component (Bassig et al., 2015); while others appear to be due to the significant alterations in the immune systems of people infected H.I.V., or afflicted with various autoimmune diseases (Cáceres et al., 2010; Liang et al., 2014). Although many hypotheses have been raised and investigated, to date, no environmental exposures have been established to cause lymphoma (IARC, 2008). Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 6 Leukemias also vary according to type, prevalence, etiologies, and clinical courses (Jandl, 1996). Although not specified by EHHI, as noted above, I suspect that most of the leukemias in the soccer players (at least, in the younger players) are the type known as acute lymphocytic leukemia (ALL). This is important because ALL — as opposed to a major leukemia-­‐type in adults, namely acute myelogenous leukemia (AML) — is not known to be caused by overexposures to chemicals, such as benzene, nor by chronic exposure to the chemicals present in cigarette smoke (IARC, 2004). More generally, no type of cancer in adolescents is known to be caused by overexposure to chemicals. Instead, many of these cancer-­‐cases are known or believed to occur spontaneously, or to be caused by factors common to us all (Lynch, 2010; Matés et al., 2012; Tomasetti et al., 2013; Tomasetti and Vogelstein, 2015). Some cases of cancers in adolescents appear to be due to infections with viruses such as Epstein-­‐Barr virus (EBV); and some are due to inherited genetic mutations (IARC, 2008). EHHI’s hypothesis with regard to crumb rubber and cancer Turning back to EHHI’s apparent hypothesis with regard to crumb rubber and cancer, I begin by noting that it is of course true that tires are industrial products made with various potentially hazardous chemicals; and although tires per se are essentially inert, finely crumbled tires can release small amounts of various chemicals. In particular, synthetic rubber products tend to have a distinctive smell, caused primarily by release of small amounts of volatile amines and organic sulfur compounds (Ambelong, 1963). These compounds are more odorous than they are toxic, and they are certainly not known or reasonably expected to pose a risk of cancer, regardless of the level of exposure. Rather than focusing on actual, measured emissions from crumb rubber, EHHI raises the specter of two other chemicals, which, at very high levels of exposures, can indeed cause cancer. As quoted above, EHHI writes: It is important to note the predominance of lymphomas and leukemias [among the 95 cases]. 1,3 butadiene is connected to lymphoma and Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 7 benzene is connected to leukemia. Both of these chemicals are present in rubber tires. These statements are misleading in several ways. First, there is nothing surprising about a “predominance of lymphomas and leukemias” among young people: as noted above, these are the most common cancers in adolescents. Indeed, it would be striking if these cancer types were not prevalent in any random group of adolescents with cancer. Second, the implication that crumb rubber is somehow a source of people’s exposures to the chemicals 1,3-­‐butadiene and benzene — let alone a significant source — is entirely incorrect. It is true that 1,3-­‐butadiene is used to make synthetic rubber (for tires and other products), but it is also used up in this process, in that it reacts with another chemical, styrene, to form a stable polymer. This stable polymer is no more a source of exposure to 1,3-­‐butadiene than, say, a thoroughly baked cake is a source of exposure to raw eggs. Nor do tires “contain” benzene: instead, some tire building-­‐machine operations rely on solvents that do contain small amounts (less than 1%) of benzene, but this benzene is not incorporated into the tire, and thus not into crumb rubber derived from tires. It is not surprising, then, that studies of ambient air in contact with crumb rubber in-­‐filled synthetic turf fields have reported either (i) no detectable concentrations of 1,3-­‐
butadiene or benzene, or (ii) only the very low-­‐level concentrations found throughout suburban and urban environments (Dye et al., 2006; Norwegian Pollution Control Authority, 2006; Moretto, 2007; Denly et al., 2008; Lim and Walker, 2009; Li et al., 2010; Schilirò et al., 2012). As noted by researchers Schilirò et al. (2012), “On the basis of environmental monitoring, artificial turf football fields present no more exposure risks than the rest of the city.” Third, as just suggested, all of us are exposed to very small concentrations of both 1,3-­‐
butadiene and benzene in ordinary outdoor air, every day. This is because both chemicals are present in the exhaust from automobiles and from several other common sources. However, the evidence that benzene can cause leukemia (and again, only AML, and not ALL of childhood, and not lymphoma) does not come from these common, low-­‐
level, environmental exposures, but instead from massive exposures experienced by Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 8 workers inside poorly ventilated factories, prior to the institution of modern industrial hygiene (Graham et al., 1988). It is entirely misleading to conflate these genuinely dangerous, historical, occupational settings with any outdoor environments, even on heavily trafficked roads, for example, let alone on playing fields. Finally, although EHHI claims that 1,3-­‐butadiene “is connected to lymphoma,” in fact it, like benzene, is known to cause leukemia (AML) and not lymphoma; and, again, it is known to do so in over-­‐exposed factory workers (Delzell et al., 1996), but not known to do so in the public at large, which experiences vastly smaller, environmental exposures. Theoretical risks of cancer from crumb rubber in-­‐filled synthetic turf fields Although benzene and 1,3-­‐butadiene are not among them, other potentially carcinogenic chemicals are present in crumb rubber (as they are in ordinary dirt), and several studies have sought to estimate the degree of health-­‐risk, if any, associated with these chemicals. For example, Van Rooij and Jongeneelen (2010) studied young-­‐adult male soccer players following intensive contact with crumb rubber-­‐filled synthetic turf. The researchers sought to determine whether this contact would lead to increased exposures to polycyclic aromatic hydrocarbons (PAHs). The researchers found that it did not. They concluded, “If there is any exposure, then the uptake is very limited and within the range of uptake of PAH from environmental sources and/or diet.” This was the case despite the fact that the athletes “had black residue of crumb dust on knees, hand palms and elbows . . . [confirming] that skin contact had occurred to dust of the tire crumb rubber.” A recently published study from New Jersey’s state medical school (The Robert Wood Johnson Medical School) provides additional information. In particular, Pavilonis and colleagues (2014) subjected samples of both new and turf field-­‐aged crumb rubber to extractions with solutions of synthetic sweat, synthetic lung fluid, and synthetic digestive fluid. They analyzed the types and amounts of chemicals that appeared in these synthetic biofluids, and then assessed whether children’s and adults’ exposures to these chemicals would be risky. Their results were negative: that is, health risks to children and adults from extensive contact with crumb rubber were found to range from none to negligible. Small amounts of potentially carcinogenic metals were detected in the crumb Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected] Page 9 rubber-­‐extracts, but the theoretical risks associated with these were all less than one in one million, “and therefore risk was considered negligible.” Earlier scientific studies and health risk-­‐assessments have reported similar results (Birkholz et al., 2003; Norwegian Institute of Public Health, 2006; Hoftstra, 2007; Ledoux, 2007; Johns, 2008). Conclusion Overall, then, for several reasons, I find no reliable basis for the notion that crumb rubber in-­‐filled synthetic turf fields pose a significant risk of cancer. I find no merit in EHHI’s apparent hypothesis as to how and why soccer players have developed cancer at excess rates. If these players do constitute a cancer-­‐cluster — and, again, one cannot say one way or the other with the limited information at hand — then this cluster has almost certainly arisen entirely by chance, as have essentially all of the others. * * * * * Thank you again for the opportunity to have considered this matter. Please feel free to call or email me with any questions or concerns. References Ambelang, J. C.; Kline, R. H.; Lorenz, O. M.; Parks, C. R.; Wadelin, C.; Shelton, J. R. (1963). Antioxidants and antiozonants for general purpose elastomers. Rubber Chem. Technol. 36 (5), 1497−1541. Bassig BA, Cerhan JR, Au WY, Kim HN, Sangrajrang S, Hu W, Tse J, Berndt S, Zheng T, Zhang H, Pornsopone P, Lee JJ, Kim HJ, Skibola CF, Vijai J, Burdette L, Yeager M, Brennan P, Shin MH, Liang R, Chanock S, Lan Q, Rothman N. Genetic susceptibility to diffuse large B-­‐cell lymphoma in a pooled study of three Eastern Asian populations. Eur J Haematol. 2015 Jan 22. Birkholz, D. A.; Belton, K. 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renewing tissues originate prior to tumor initiation. Proc Natl Acad Sci U S A. 2013 Feb 5;110(6):1999-­‐2004. Trumbo, C. W. (2000). Public requests for cancer cluster investigations: A survey of state health departments. American Journalof Public Health, 90, 1300–1303. Van Rooij, J. G.; Jongeneelen, F. J. (2010). Hydroxypyrene in urine of football players after playing on artificial sports field with tire crumb infill. Int. Arch. Occup. Environ. Health, 83 (1), 105−110. Ward E, DeSantis C, Robbins A, Kohler B, Jemal A. (2014). Childhood and adolescent cancer statistics, 2014. CA: A Cancer Journal for Clinicians. 64(2):83-­‐103. Laura C. Green, Ph.D., D.A.B.T., Consulting toxicologist 106 Sumner Road, Brookline, Massachusetts 02445 617-­‐835-­‐0093 [email protected]